Implantable electrodes containing polyoxometalate anions and methods of manufacture and use

ABSTRACT

An implantable device includes at least one electrode comprising a conductive base and polyoxometalate anions disposed on or within the conductive base; and at least one conductor attached to the at least one electrode for conducting electrical energy to the at least one electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. Patent ApplicationSerial No. 11/614,870 filed on Dec. 21, 2006, which is incorporatedherein by reference.

FIELD

The invention is directed to implantable electrodes, devices thatinclude the electrodes, and methods of manufacturing and using theelectrodes and devices. In addition, the invention is directed toimplantable electrodes with polyoxometalate anions, devices that includethe electrodes, and methods of manufacturing and using the electrodesand devices.

BACKGROUND

Tissue stimulation using implantable electrodes has importanttherapeutic uses. For example, implantable pacemakers, defibrillators,and cardioverters stimulate the muscle tissue of the heart. Implantableneurostimulators have been developed to provide therapy for a variety ofdisorders, as well as other treatments. Implantable neurostimulators canbe used in neurological therapy by stimulating nerves or muscles, forexample, spinal cord tissue or brain tissue. Other uses of implantableneurostimulators include, but are not limited to, treatment for urinaryor faecal urge incontinence by stimulating nerve fibers proximal to thepudendal nerves of the pelvic floor, treatment for erectile and othersexual dysfunctions by stimulating the cavernous nerve(s), treatment forreduction of pressure sores or venous stasis, etc. Other uses forimplantable electrodes include muscle stimulation, gastroparesistreatment, wound healing, retinal and sub-retinal treatment, recording,sensing, and monitoring.

Stimulation systems typically include implantable electrodes attachedto, or disposed adjacent to, the tissue to be stimulated. Somestimulation systems, including at least some spinal cord stimulationsystems, have an implantable percutaneous, cuff, or paddle lead withmultiple electrodes, as well as a separate control module that housesthe power source and pulse generator. In many configurations, thiscontrol module is also implantable.

Implantable microstimulators, such as the BION® device (available fromAdvanced Bionics Corporation, Sylmar, Calif.), have exposed electrodesand a small, often cylindrical, housing that contains the electroniccircuitry and power source that produce electrical pulses at theelectrodes for stimulation of the neighboring tissue. Once implanted, itis often preferable that the microstimulator can be controlled and/orthat the electrical source can be charged without removing themicrostimulator from the implanted environment.

In many instances, implantable electrodes for electrical stimulationideally should have a relatively small geometric surface area to producea lower stimulation threshold and longer battery life. However, thereduction of the geometric surface area can increase current density andpossibly exceed safe charge injection limits, which could result in, forexample, dissolution of electrode material, undesirable electrolyticredox reductions, and production of toxic chemicals. This can becounteracted by increasing the actual surface area by, for example,using porous electrode materials such as platinized platinum, iridiumoxide, titanium nitride, or sintered microspheres, or by usingelectrodes with fractal surface morphology or fractal coatings.

BRIEF SUMMARY

One embodiment is an implantable device that includes at least oneelectrode comprising a conductive base and polyoxometalate anions ortheir derivatives disposed on or within the conductive base; and atleast one conductor attached to the at least one electrode forconducting electrical energy to the at least one electrode.

Another embodiment is a method of making an implantable electrode byforming a conductive base; and disposing polyoxometalate anions on orwithin the conductive base.

Yet another embodiment is a stimulation system that includes a housing;a power source disposed in the housing; at least one electrodecomprising a conductive base and polyoxometalate anions disposed on orwithin the conductive base; and at least one conductor attached to theat least one electrode and to the power source to provide electricalenergy to the at least one electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1A is a schematic cross-sectional view of one embodiment of animplantable electrode, according to the invention;

FIG. 1B is a schematic cross-sectional view of a second embodiment of animplantable electrode, according to the invention;

FIG. 1C is a schematic cross-sectional view of a third embodiment of animplantable electrode, according to the invention;

FIG. 2 is a schematic top view of one embodiment of a stimulation systemwith a percutaneous electrode lead, according to the invention;

FIG. 3 is a schematic top view of one embodiment of a stimulation systemwith a paddle electrode lead, according to the invention;

FIG. 4 view of one embodiment of a microstimulator, according to theinvention; and

FIG. 5 is a schematic block diagram of components for one embodiment ofa stimulation system, according to the invention.

DETAILED DESCRIPTION

The invention is directed to implantable electrodes, devices thatinclude the electrodes, and methods of manufacturing and using theelectrodes and devices. In addition, the invention is directed toimplantable electrodes with polyoxometalate anions, devices that includethe electrodes, and methods of manufacturing and using the electrodesand devices.

Suitable devices with implantable electrodes include, but are notlimited to, therapeutic devices such as implantable pacemakers,defibrillators, cardioverters, neurostimulators, microstimulators, andmuscle stimulators, all of which are electrostimulation device, as wellas sensors and other diagnostic, monitoring and recording devices (forexample, glucose sensors or seizure warning systems), controlled drugdelivery systems, and therapeutic agent delivery systems. In someembodiments, the implantable device can include an electrode lead withone or more electrodes disposed on a distal end of the lead and one ormore terminals disposed on a proximal end of the lead. Electrodes leadsinclude, for example, percutaneous leads, cuff leads, and paddle leads.Examples of stimulation systems with electrode leads are described in,for example, U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029; 6,609,032;and 6,741,892; and U.S. patent applications Ser. Nos. 11/238,240;11/319,291; 11/327,880; 11/375,638; 11/393,991; and 11/396,309, all ofwhich are incorporated herein by reference.

Examples of implantable microstimulators are described in U.S. Pat. Nos.5,193,539; 5,193,540; 5,312,439; and 6,051,017; U.S. Patent ApplicationPublication No. 2004/059392; U.S. patent application Ser. Nos.11/040,209; 11/056,762; 11/084,368; and 11/238,240 and PCT PatentApplications Publication Nos. 98/37926; 98/43700; and 98/43701, all ofwhich are incorporated herein by reference. The BION™ microstimulator,available from Advanced Bionics Corporation, Sylmar, Calif., is anexample of a microstimulator.

The implantable electrode includes a conductive base and polyoxometalateanions, preferably as anion clusters, disposed on or within theconductive base. The polyoxometalate anions can be included, forexample, in a coating, within the material of the conductive base,attached to the conductive base, or any combination thereof. For atleast some embodiments, the implantable electrode with polyoxometalateanions can have improved capacitance, polarization, electrochemicalperformance, or stability (or any combination of these improvements)when compared to similar implantable electrodes without thepolyoxometalate anions. The polyoxometalate anions may alsosignificantly increase the number of surface sites for electrodematerials or coatings.

The polyoxometalate anions can have the formula[X_(x)M_(y)Q_(w)O_(z)]^(q−). M and Q are transition metals; X is aheteroatom and can be, for example, P, Si, B, Ge, As, S, Al or Sb; x, y,w, and z are integers where y and z are at least 5 and x and w may be 0;and q is an integer that represents the charge of the anion.

M and Q are preferably Ta, V, Mo, Co, Cr, Ni, Nb, W, Ti, Fe, Ir, Ru, Zr,Mn, Zn, Pd, Sn, Pt or Cu. More preferably, M is Mo, V, W, Nb, Ir, Zr,Fe, Ru, Ti, or Ta and even more preferably, M is Mo or W. Morepreferably, Q, if present, is Zn, Ti, Zr, Fe, Co, or Pd. X, if present,is preferably P, B, or Si. x is typically in the range of 0 to 8 andpreferably in the range of 0 to 5. y is typically in the range of 5 to30 and preferably in the range of 5 to 20. w is typically in the rangeof 0 to 12 and preferably in the range of 0 to 10. z is typically atleast 10, preferably in the range of 10 to 80, and more preferably inthe range of 18 to 62. q is typically in the range of 1 to 10 andpreferably in the range of 1 to 6.

In addition, polyoxometalate anions include those in which one or moreof the oxygen atoms are replaced with other covalently bondedsubstituents. Such polyoxometalate anions have the formula[X_(x)M_(y)Q_(w)O_(z)R_(r)]^(q−) where R a covalently bonded substituentand r is an integer typically ranging from 0 to 10. Examples include,but are not limited to, organoimido derivatives such as those describedin Xu, et al., Angew. Chem., 114, 4303-6 (2002); Roesner, et al.,Inorganica Chimica Acta, 324, 34-47 (2003); and Lu, et al., Chem. Mater.17, 402-408 (2005), all of which are incorporated herein by reference.In one embodiment, the organoimido substituent is ═NR¹ where R¹ issubstituted or unsubstituted aryl. The substituents on the aryl, if any,can be ortho-, para-, or meta-substituents (or any combination thereofif there are two or more substituents.) Examples of suitablesubstituents for the aryl moiety include, but are not limited to, alkyl,aralkyl, alkoxy, halo, hydroxy, alkenyl, alkynyl, nitro, cyano, amino,and the like. Any of these substituents may be substituted orunsubstituted.

Another example of the R substituent is —Si—R² as discussed, forexample, in Mayer et al., Chem. Mater., 12, 257-60 (2000), incorporatedherein by reference. R² can be any organic substituent includingsubstituted or unsubstituted alkyl or aryl. In one embodiment, R² can bea monomeric unit that can be polymerized to form a cross-linked polymernetwork, such as a polymethacrylate (e.g., poly(ethyl methacrylate)) orpolystyrene.

The polyoxometalate anions include, but are not limited to, those anionswith the “Keggin” structure (examples: (BW₁₂O₄₀)⁵⁻ and (SiW₁₂O₄₀)⁴⁻) or“Dawson” structure (example: (P₂W₁₈O₆₂)⁶⁻). Other examples of structuresinclude, but are not limited to, those discussed in Kaba, et al., Inorg.Chem. 37, 398-406 (1998), incorporated herein by reference. When x and ware 0, the anion ([M_(y)O_(z)]^(q−)) is sometimes referred to as an“isopoly” anion. When x≠0, the anion is sometimes referred to as a“heteropoly” anion.

Optionally, the polyoxometalate anions may also have one of moreassociated cations including, but not limited to, H⁺, alkali metalcations, NH₄ ⁺, alkaline earth cations, transition metal cations, andcationic organic compounds. Suitable cationic organic compounds include,for example, cationic polymers such as those with cationic monomerunits, for example, polypyrrole, polythiophene, polyaniline, polyfurane,polyacetylene, chitosan, polyetherimide, and the like. The cationicorganic compounds can also be non-polymeric. One example is the Hbpy⁺cation, where bpy is 2,4-bipyridine, as described, for example, in Hanet al., Electrochimica Acta, 51, 218-224 (2005), incorporated herein byreference.

The polyoxometalate anions may also be formed on, or otherwise disposedon, a wire, fiber, or other object including, but not limited to,nanowires, nanofibers, and other nanoobjects.

For an implantable electrode, the polyoxometalate anions used in theelectrode are preferably biocompatible. Such biocompatibility can takeinto account the expected length of time that the electrode isimplanted, as well as the retention of the polyoxometalate anion, orconstituents (e.g., atoms or ions) thereof, by the electrode over theimplantation period.

FIG. 1A illustrates one embodiment of an implantable electrode 50. Theimplantable electrode includes a conductive base 52 and a coating 54.The conductive base can be any biocompatible, conductive materialincluding, but not limited to, metals, alloys, metal oxides, metalnitrides, metal carbides, metal borides, carbon, doped silicon, andconductive polymers (including polymers with conductive fillers), aswell as any combinations thereof. The conductive base may be, forexample, a unitary body or can contain multiple conductive layers.

The coating 54 includes the polyoxometalate anions 56 and a carrier 58.The polyoxometalate anions are typically dispersed within the carrier.The polyoxometalate anions can be uniformly or non-uniformly dispersedwithin the carrier. The polyoxometalate anions may all have the samechemical composition or anions with two or more different chemicalcompositions can be used together.

The carrier 58 is preferably a biocompatible, conductive material suchas a conductive polymer, polyelectrolyte, ionomer, polymer-ceramichybrid (and other inorganic-organic hybrids), or conductive ceramic(e.g., iridium oxide or ruthenium oxide, as well as other conductiveoxides, conductive nitrides, or mixtures thereof), or any combinationthereof. Preferably, the conductive material can form cationic sites.Examples of suitable conductive polymer materials include, but are notlimited to, polypyrrole, polythiophene, polyaniline, polyfurane,polyacetylene, cationic polyelectrolytes, polyetherimide (PEI),poly(diallyldimethlyammonium chloride) (PDDA), poly(allylaminehydrochloride) (PAH), chitosan, polylysine, and the like.

The coating 54 can be formed in any manner including by depositing thecarrier and polyoxometalate anions onto the conductive base using anycoating or deposition method such as, for example, dip coating, dripcoating, spin coating, curtain coating, electropolymerization,layer-by-layer coating alternating between the carrier and thepolyoxometalate anions, Langmuir-Blodget films, sol-gel, self assembly,electro-spraying, magneto-electrophoresis, or any other coating method.In some embodiments, the carrier is a polymeric material formed usingmonomer materials that are polymerized prior to, or after deposition, onthe conductive base. The polyoxometalate anions can be incorporated intothe coating prior to, during, or after polymerization. In oneembodiment, the monomer material is disposed on the conductive base withthe polyoxometalate anions and the monomer material is then polymerizedusing any polymerization technique including, but not limited to,electrochemical polymerization, vapor growth, or plasma polymerization.In another embodiment, the polymer is formed prior to deposition on theconductive base.

In other embodiments, the polyoxometalate anions can be doped into analready formed coating using any technique. Examples of suitabletechniques include, but are not limited to, diffusion techniques andacid-base doping techniques.

The coating may also include one or more additives. Examples ofadditives include fillers, colorants, anti-oxidants, plasticizers,accelerants, initiators, nanoparticles, therapeutic agents,biomolecules, and the like.

Any suitable coating thickness can be used. For example, the coating canhave a thickness in the range of 0.5 to 15 micrometers.

The level of polyoxometalate anions in the coating can be selected toprovide desired properties. For example, in some embodiments, thepolyoxometalate anions may be up to 40 wt. % of the coating (although itwill be understood that other embodiments may include even more of thepolyoxometalate anions). In at least some embodiments, thepolyoxometalate anions may be in the range of 5 wt. % to 40 wt. % of thecoating. In at least some embodiments using a polymeric carrier, theratio of carrier monomers to polyoxometalate anions is at least 10:1 andmay be in the range of 4:1 to 1:1.

Physical, electrical, and chemical characteristics of the coating 54 andimplantable electrode 50 can be controlled or modified by a variety offactors including, but not limited to, the selection of particularpolyoxometalate anion(s) or derivative(s) thereof and carrier, the levelof polyoxometalate anions in the coating, the relative thickness of thecoating, and the use of additives. For example, electricalcharacteristics such as, for example, capacitance, impedance, chargetransfer resistance, or faradaic resistance, can be controlled ormodified by selecting the chemical composition and doping level of thepolyoxometalate anions. In some embodiments, the level ofpolyoxometalate anions in the coating can be adjusted by co-doping withother anions.

FIG. 1B illustrates another implantable electrode 50 withpolyoxometalate anions 56 dispersed in the material of the conductivebase 52. The anions can be uniformly or non-uniformly dispersed in theconductive base.

Polyoxometalate anions can be included with the formation of theconductive base 52. For example, the polyoxometalate anions can beincluded as the conductive base is formed. Examples of suitabletechniques for forming the conductive base with polyoxometalate anionsinclude, but are not limited to, sputtering, electrodeposition, sol-gelformation, co-deposition, self-assembly, ion-implantation, or multilayerdeposition (with individual layers of polyoxometalate anions andconductive base). Examples of suitable materials for the sol-gelformation of a conductive base include, but are not limited to, IrO₂,TiO₂—IrO₂, IrO₂—TaO₂, platinized platinum, Pt, Pt—Ir, TiN, carbon,silicon, RuO₂ and the like. In other embodiments, the polyoxometalateanions can be incorporated into the conductive base after it is formedusing, for example, diffusion and acid-base doping techniques.

Physical, electrical, and chemical characteristics of the implantableelectrode 50 can be controlled or modified by a variety of factorsincluding, but not limited to, the selection of particularpolyoxometalate anion(s) and carrier and the level of polyoxometalateanions in the conductive base.

FIG. 1C illustrates another implantable electrode 50 withpolyoxometalate anions attached to the material of the conductive base52. The polyoxometalate anions can be, for example, pendant surfaceligands attached via ionic or covalent bonds or any combination thereof.In some embodiments, the surface of the conductive base 52 may beprepared for attachment of the polyoxometalate anions. For example, thesurface may be chemically or mechanically treated to produce radicals onthe surface. In some embodiments, the conductive base may be amultilayer construction with the top layer being selected or preparedfor attachment of the polyoxometalate anions.

Physical, electrical, and chemical characteristics of the implantableelectrode 50 can be controlled or modified by a variety of factorsincluding, but not limited to, the selection of particularpolyoxometalate anion(s) and carrier and the level of polyoxometalateanions attached to the conductive base.

It will be understood that the embodiments illustrated in FIGS. 1A, 1B,and 1C can be combined together in any combination. For example, theimplantable electrode may have polyoxometalate anions disposed in theconductive base and in a coating on the conductive base.

FIGS. 2 and 3 illustrate schematically embodiments of a stimulationsystem 100 that includes a control module (e.g., a stimulator or pulsegenerator) 102, an array body 104, and at least one lead body 106coupling the control module to the electrode array. The array body 104and the lead body 106 form a lead. In FIG. 2 the lead is a percutaneouslead and in FIG. 3 the lead is a paddle lead. It will be understood thatthe stimulation system for can include more, fewer, or differentcomponents and can have a variety of different configurations includingthose configurations disclosed in the references cited herein. Thestimulation system or selected components of the stimulation system,including one or more of the lead body 106, the array body 104 and thecontrol module 102, can be implanted into the body.

The array body 104 includes multiple implantable electrodes 154. One ormore of the implantable electrodes 154 include polyoxometalate anions asdescribed above. In some embodiments, all of the implantable electrodesinclude polyoxometalate anions.

A conductor (not shown) is attached to each of the electrodes 154 andextends along the lead body 106 to the control module 102 to conductelectrical pulses from the control module to the electrode. Preferably,the conductor is attached to the back side of the electrode 154, whichis the side of the electrode 154 opposite the side that will be exposedto the body tissue. The conductors can be made of any conductivematerial. Examples of suitable material for conductors include, forexample, metals, alloys, conductive polymers, and conductive carbon. Inone embodiment, the conductors are insulated by an insulating materialexcept where the conductor makes contact with the electrode 154. Theinsulating material may be any material that is a poor conductor of anelectrical signal, including, for example, Teflon™, non-conductivepolymers, nylon, Mylar, polyether bloc amides (such as the PEBAX™ resinsavailable from Arkema, Inc., Philadelphia, Pa.), polytetrafluoroethylene(PTFE), polyimide, polyurethane, and composite materials. The conductorsmay be attached to the electrodes by any method including, for example,resistance welding, laser welding, conductive epoxy, and the like.Preferably, the conductors are attached to the electrodes 154 by amethod that results in a durable attachment of the conductors to theelectrodes 154 under expected usage conditions.

The lead body 106 and array body 104 (excluding the electrodes 154) aretypically made of a non-conductive material such as, for example,silicone, polyurethane, polyetheretherketone (PEEK), epoxy, and thelike. Optionally, the lead body may include one or more lumens throughwhich the conductors pass or through which a drug or other medicationcan pass to the site of stimulation near the electrodes 154. The leadbody 106 also may include a connector (not shown) for attachment to thecontrol module 102 with contacts to connect the conductors tocorresponding contacts of the control module.

The control module 102 typically includes a housing 114 with anelectronic subassembly 110 and, in at least some embodiments, a powersource 112 disposed within a chamber in the housing. Preferably, thehousing is resistant to moisture penetration into the chamber containingthe electronic subassembly and power source. In some embodiments, watermay diffuse through the housing. Preferably, the diffused water isrelatively pure, without substantial ionic content, as deionized wateris relatively non-conductive. The housing 114 may be made of anybiocompatible material including, for example, glass, ceramics, metals,polymers, and combinations thereof. The thickness of the walls of thehousing may also impact the moisture permeability of the housing. Aminimum thickness needed to achieve a particular degree of resistance tomoisture transport will often depend on the material selected for thehousing, as well as any additives.

Optionally, the housing 114 can be covered, in full or in part, with acoating. The coating can be provided to improve or alter one or moreproperties of the housing 114 including, for example, biocompatibility,hydrophobicity, moisture permeability, leaching of material into or outof the housing, and the like. In one embodiment, a coating can beapplied which contains a compound, such as, for example, a drug,prodrug, hormone, or other bioactive molecule, that can be released overtime when the stimulator is implanted. In another embodiment, thehousing itself may include such a compound to be released over timeafter implantation.

FIG. 4 illustrates one embodiment of an implantable microstimulator 170.The implantable microstimulator 170 includes a housing 172, animplantable electrode 154 that contains polyoxometalate anions, anoptional second electrode 176 (which may or may not containpolyoxometalate anions), a power source 112, an electronics subassembly110, and an optional antenna 124. Other embodiments of an implantablemicrostimulator may include more or fewer components. It will beunderstood that the power source 112 and/or components of theelectronics subassembly 110 and/or the optional antenna 124 can beprovided outside of the housing in a separate unit and coupled to theimplantable microstimulator by a lead.

The housing 172 can be formed of any material that resists the transportof moisture into the interior of the housing and is sufficiently sturdyto protect the components in the interior of the housing from damageunder expected implantation and usage conditions. Suitable materials forthe housing 172 (or a portion of the housing) include, for example,metals, ceramics, glass, plastics, and combinations thereof. The housingof the microstimulator is preferably composed of biocompatiblematerials.

Optionally, the housing 172 can be covered, in full or in part, with acoating. The coating can be provided to improve or alter one or moreproperties of the housing including, for example, biocompatibility,hydrophobicity, conductivity, moisture permeability, leaching ofmaterial into or out of the housing, and the like. The optional coatingcan be a polymer material, inorganic material, or organic material. Asan example, a silicone coating may be used to improve biocompatibility.In yet another example, a coating can be applied which contains acompound, such as, for example, a drug, prodrug, hormone, or otherbioactive molecule, that can be released over time when themicrostimulator is implanted.

In at least some embodiments, the length of the microstimulator is nogreater than 30 mm. Typically the length of the microstimulator is inthe range of 10 to 30 mm.

The microstimulator can be implanted into the body tissue using avariety of methods including surgical methods. In some embodiments, theimplantable electrode can be implanted using a hypodermic needle orother insertion cannula. Examples of insertion techniques can be foundin U.S. Pat. No. 6,051,017.

FIG. 5 is a schematic overview of one embodiment of components of asystem for stimulation (for example, the stimulation systems of FIGS. 2and 3 or the microstimulator of FIG. 4), including an electronicsubassembly 110 (which may or may not include the power source 112),according to the invention. It will be understood that the system forstimulation and the electronic subassembly 110 can include more, fewer,or different components and can have a variety of differentconfigurations including those configurations disclosed in thestimulator references cited herein. Some or all of the components of thesystem for stimulation can be positioned on one or more circuit boardsor similar carriers within a housing of a stimulator, if desired.

Any power source 112 can be used including, for example, a battery suchas a primary battery or a rechargeable battery. Examples of other powersources include super capacitors, nuclear or atomic batteries,mechanical resonators, infrared collectors, thermally-powered energysources, flexural powered energy sources, bioenergy power sources, fuelcells, bioelectric cells, osmotic pressure pumps, and the like includingthe power sources described in U.S. Patent Application Publication No.2004/0059392, incorporated herein by reference.

As another alternative, power can be supplied by an external powersource through inductive coupling via the optional antenna 124 or asecondary antenna. The external power source can be in a device that ismounted on the skin of the user or in a unit that is provided near thestimulator user on a permanent or periodic basis.

If the power source 112 is a rechargeable battery, the battery may berecharged using the optional antenna 124, if desired. Power can beprovided to the battery 112 for recharging by inductively coupling thebattery through the antenna to a recharging unit 210 external to theuser. Examples of such arrangements can be found in the stimulatorreferences identified above.

In one embodiment, electrical current is emitted by the electrodes 154(and 176) to stimulate, for example, motor nerve fibers, muscle fibers,or other body tissues near the stimulator. The electronic subassembly110 provides the electronics used to operate the stimulator and generatethe electrical pulses at the electrodes 154 (and 176) to producestimulation of the body tissues.

In the illustrated embodiment, a processor 204 is generally included inthe electronic subassembly 110 to control the timing and electricalcharacteristics of the stimulator. For example, the processor can, ifdesired, control one or more of the timing, frequency, strength,duration, and waveform of the pulses. In addition, the processor 204 canselect which electrodes can be used to provide stimulation, if desired.In some embodiments, the processor may select which electrode(s) arecathodes and which electrode(s) are anodes. This process may beperformed using an external programming unit, as described below, thatis in communication with the processor 204.

Any processor can be used. For example, the processor can be as simpleas an electronic device that produces pulses at a regular interval orthe processor can be complex and capable of receiving and interpretinginstructions from an external programming unit 208 that allowmodification of pulse characteristics. In the illustrated embodiment,the processor 204 is coupled to a receiver 202 which, in turn, iscoupled to the optional antenna 124. This allows the processor toreceive instructions from an external source to direct the pulsecharacteristics and the selection of electrodes, if desired.

In one embodiment, the antenna 124 is capable of receiving signals(e.g., RF signals) from an external telemetry unit 206 which isprogrammed by a programming unit 208. The programming unit 208 can beexternal to, or part of, the telemetry unit 206. The telemetry unit 206can be a device that is worn on the skin of the user or can be carriedby the user and can have a form similar to a pager or cellular phone, ifdesired. As another alternative, the telemetry unit may not be worn orcarried by the user but may only be available at a home station or at aclinician's office. The programming unit 208 can be any unit that canprovide information to the telemetry unit for transmission to thestimulator. The programming unit 208 can be part of the telemetry unit206 or can provide signals or information to the telemetry unit via awireless or wired connection. One example of a suitable programming unitis a computer operated by the user or clinician to send signals to thetelemetry unit.

The signals sent to the processor 204 via the antenna 124 and receiver202 can be used to modify or otherwise direct the operation of thestimulator. For example, the signals may be used to modify the pulses ofthe stimulator such as modifying one or more of pulse duration, pulsefrequency, pulse waveform, and pulse strength. The signals may alsodirect the stimulator to cease operation or to start operation or tostart charging the battery. In other embodiments, the electronicsubassembly 110 does not include an antenna 124 or receiver 202 and theprocessor operates as programmed.

Optionally, the stimulator may include a transmitter (not shown) coupledto the processor and antenna for transmitting signals back to thetelemetry unit 206 or another unit capable of receiving the signals. Forexample, the stimulator may transmit signals indicating whether thestimulator is operating properly or not or indicating when the batteryneeds to be charged. The processor may also be capable of transmittinginformation about the pulse characteristics so that a user or cliniciancan determine or verify the characteristics.

The optional antenna 124 can have any form. In one embodiment, theantenna comprises a coiled wire that is wrapped at least partiallyaround the electronic subassembly within or on the housing.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed and desired to be protected by Letters Patent of theUnited States is:
 1. An implantable lead, comprising: an elongate leadbody comprising a distal portion and a proximal portion; a plurality ofelectrodes disposed on the distal portion of the lead body, at least oneof the electrodes comprising a conductive base and polyoxometalateanions disposed on or within the conductive base, wherein thepolyoxometalate anions comprise anions having the formula[X_(x)M_(y)Q_(w)O_(z)]^(q−) or the formula[X_(x)M_(y)Q_(w)O_(z)R_(r)]^(q−) wherein M and Q are independentlyselected from Ta, V, Mo, Co, Cr, Ni, Nb, W, Ti, Fe, Ir, Ru, Zr, Mn, Zn,Pd, Sn, Pt, or Cu; X is selected from P, Si, B, Ge, As, or Sb; R is acovalently bonded substituent; x, y, w, z, and r are integers, wherein yand z are at least 5 and x, w, and r are at least 0; and q is an integerthat represents the charge of the anion; and a plurality of conductorsdisposed in the lead body and attached to the plurality of electrodesfor conducting electrical energy to the plurality of electrodes forstimulation of adjacent tissue when implanted.
 2. The implantable leadof claim 1, wherein the lead is a percutaneous lead with the pluralityof electrodes arranged sequentially along the distal portion of the leadbody.
 3. The implantable lead of claim 1, wherein the lead is a paddlelead comprising an array body at the distal portion of the lead body,wherein the plurality of electrodes are arranged as an array on thearray body.
 4. The implantable lead of claim 1, further comprising acoating disposed on the conductive base, wherein at least a portion ofthe polyoxornetalate anions are dispersed in the coating.
 5. Theimplantable lead of claim 4, wherein the coating comprises a conductivepolymer carrier within which the portion of the polyoxometalate anionsare dispersed.
 6. The implantable lead of claim 5, wherein theconductive polymer carrier is selected from polypyrrole, polythiophene,polyaniline, polyfurane, polyacetylene, polyetherimide,poly(diallyldimethylammonium chloride), poly(allylamine hydrochloride),chitosan, or polylysine.
 7. The implantable lead of claim 1, wherein atleast a portion of the polyoxometalate anions are dispersed within theconductive base.
 8. The implantable lead of claim 1, wherein at least aportion of the polyoxometalate anions are attached to a surface of theconductive base.
 9. The implantable lead of claim 1, wherein each of theelectrodes comprises the conductive base and the polyoxometalate anions.10. The implantable lead of claim 1, wherein the plurality of electrodesform an array.
 11. A method of stimulating tissue, the methodcomprising: implanting an electrode into tissue, the electrodecomprising a conductive base and polyoxometalate anions disposed on orwithin the conductive base, wherein the polyoxometalate anions compriseanions having the formula [X_(x)M_(y)Q_(w)O_(z)]^(q−) or the formula[X_(x)M_(y)Q_(w)O_(r)]^(q−) wherein M and Q are independently selectedfrom Ta, V, Mo, Co, Cr, Ni, Nb, W, Ti, Fe, Ir, Ru, Zr, Mn, Zn, Pd, Sn,Pt, or Cu; X is selected from P, Si, B, Ge, As, or Sb; R is a covalentlybonded substituent; x, y, w, z, and r are integers, wherein y and z areat least 5 and x, w, and r are at least 0; and q is an integer thatrepresents the charge of the anion; coupling the electrode to a powersource and an electronic subassembly configured and arranged to controldelivery of electrical energy from the power source to the electrode;and delivering electrical energy from the power source to the electrodeto stimulate the tissue.
 12. The method of claim 11, wherein theelectrode is disposed on an implantable lead, wherein implanting theelectrode into tissue comprises implanting the implantable lead with theelectrode into tissue.
 13. The method of claim 11, wherein a controlmodule comprises the power source and the electronic subassembly. 14.The method of claim 13, further comprising implanting the controlmodule.
 15. The method of claim 11, wherein a microstimulator comprisesthe electrode, the power source, and the electronic subassembly, whereinimplanting the electrode into tissue comprises implanting themicrostimulator into tissue.
 16. An impiantabie electrode, comprising: aconductive base; and polyoxometalate anions disposed on or within theconductive base, wherein the polyoxometalate anions comprise anionshaving the formula [X_(x)M_(y)Q_(w)O_(z)]^(q−) or the formula[X_(x)M_(y)Q_(w)O_(z)R_(r)]^(q−) wherein M and Q are independentlyselected from Ta, V, Mo, Co, Cr, Ni, Nb, W, Ti, Fe, It, Ru, Zr, Mn, Zn,Pd, Sn, Pt, or Cu; X is selected from P, Si, B, Ge, As, or Sb; R is acovalently bonded substituent; x, y, w, z, and r are integers, wherein yand z are at least 5 and x, w, and r are at least 0; and q is an integerthat represents the charge of the anion; wherein the electrode isconfigured and arranged for implantation into a patient for delivery ofelectrical stimulation to tissue of the patient adjacent the electrode.17. The electrode of claim 16, further comprising a coating disposed onthe conductive base, wherein at least a portion of the polyoxometalateanions are dispersed in the coating.
 18. The electrode of claim 17,wherein the coating comprises a conductive polymer carrier within whichthe portion of the polyoxometalate anions are dispersed.
 19. Theelectrode of claim 16, wherein at least a portion of the polyoxometalateanions are dispersed within the conductive base.
 20. The electrode ofclaim 16, wherein at least a portion of the polyoxemetalate anions areattached to a surface of the conductive base.